Spadina Subway Extension – Downsview Station to Steeles Avenue
Environmental Assessment
APPENDIX O
STORM WATER MANAGEMENT
REPORT
Spadina Subway Extension – Downsview Station to Steeles Avenue
Environmental Assessment
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
TABLE OF CONTENTS
Page
CHAPTER 1.0
SPADINA SUBWAY EXTENSION ENVIRONMENTAL
ASSESSMENT
STORMWATER MANAGEMENT REPORT
1.1
1.2
1.3
1.3.1
1.3.2
1.3.3
1.4
1.5
1.6
1.7
STUDY PURPOSE .....................................................................................................................................1
STUDY SCOPE..........................................................................................................................................3
STORMWATER MANAGEMENT DESIGN CRITERIA – CITY OF TORONTO .........................................3
Water Quality - Total Suspended Solids (TSS) ....................................................................................3
Water Quantity ....................................................................................................................................3
Water Balance .....................................................................................................................................4
PERFORMANCE STANDARDS – CITY OF VAUGHAN............................................................................5
PERFORMANCE STANDARDS – TORONTO TRANSIT COMMISSION (TTC) ........................................5
PERFORMANCE STANDARDS – TORONTO AND REGION CONSERVATION AUTHORITY (TRCA) ...5
ANALYSIS METHODOLOGY ...................................................................................................................6
CHAPTER 2.0
2.1
2.2
2.3
2.4
2.5
URS CANADA INC.
Consulting Engineers
75 Commerce Valley Drive East
Markham, Ontario
L3T 7N9
Revised February 2006
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y
Stormwater Management\013006 TTC Spadina Subway EA SWM Rpt.doc
4.1
4.2
4.3
4.4
4.5
YORK UNIVERSITY STATION SWM PLAN ..................................................................17
DESIGN REQUIREMENTS ......................................................................................................................17
QUALITY CONTROL ..............................................................................................................................17
QUANTITY CONTROL ...........................................................................................................................17
WATER BALANCE .................................................................................................................................19
EROSION AND SEDIMENT CONTROL ..................................................................................................19
CHAPTER 5.0
5.1
5.2
5.3
5.4
5.5
FINCH WEST STATION SWM PLAN...............................................................................12
DESIGN REQUIREMENTS ......................................................................................................................12
QUALITY CONTROL ..............................................................................................................................12
QUANTITY CONTROL ...........................................................................................................................15
WATER BALANCE .................................................................................................................................16
EROSION AND SEDIMENT CONTROL ..................................................................................................16
CHAPTER 4.0
Prepared By:
SHEPPARD AVENUE WEST STATION SWM PLAN ......................................................9
DESIGN REQUIREMENTS ........................................................................................................................9
QUALITY CONTROL ................................................................................................................................9
QUANTITY CONTROL .............................................................................................................................9
WATER BALANCE .................................................................................................................................11
EROSION AND SEDIMENT CONTROL ..................................................................................................11
CHAPTER 3.0
3.1
3.2
3.3
3.4
3.5
INTRODUCTION AND DESIGN STANDARDS ................................................................1
STEELES WEST STATION SWM PLAN..........................................................................20
DESIGN REQUIREMENTS ......................................................................................................................22
QUALITY CONTROL ..............................................................................................................................22
QUANTITY CONTROL ...........................................................................................................................22
WATER BALANCE .................................................................................................................................23
EROSION AND SEDIMENT CONTROL ..................................................................................................23
CHAPTER 6.0
CONSTRUCTION IMPACTS AND MITIGATION AND MONITORING ...................25
CHAPTER 7.0
CONCLUSIONS ....................................................................................................................26
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway EA
SWM Rpt.doc
URS Canada Inc.
i
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Spadina Subway Extension
Environmental Assessment
CHAPTER 1.0
2/7/2006
Stormwater Management Report
INTRODUCTION AND DESIGN STANDARDS
APPENDICES
A
B
C
1.1
TRCA’s Flood Flow Criteria Map
Rational Method Calculations
Modified Rational Method Storage Calculations
STUDY PURPOSE
As part of the Spadina Subway Extension Environmental Assessment, the construction of four
(4) subway stations and affiliated parking is proposed. Table 1.1 identifies new impervious areas
associated with these facilities. A plan showing the locations of these proposed subway stations
is provided in Exhibit 1.1.
LIST OF EXHIBITS
Page
Table 1.1 – Proposed Subway Station Descriptions
Exhibit 1.1 – Proposed Subway Station Locations........................................................................................................2
Exhibit 2.1 – Existing Drainage Conditions at the Proposed Sheppard West Station.................................................10
Location
Proposed Facility
New Impervious Area (ha)
Exhibit 3.1 – Existing Drainage Conditions at the Proposed Finch West Station.......................................................13
Exhibit 3.2 – Proposed Drainage Conditions at the Proposed Finch West Station .....................................................14
Sheppard Avenue West
Station Building
Finch West
0.2
Commuter Parking Lot
2.3
Exhibit 5.1 – Existing Drainage Conditions at the Proposed Steeles West Station.....................................................21
Passenger Pick-Up/Drop-Off
0.3
Exhibit 5.2 – Proposed Drainage Conditions at the Proposed Steeles West Station ...................................................24
Bus Terminal / Roads / Station
Building
1.2
York University Station
Station Building
0.1
Steeles West Station
East Commuter Parking Lot
5.2
Exhibit 4.1 – Existing Drainage Conditions at the Proposed York University Station ...............................................18
LIST OF TABLES
Page
Table 1.1 – Proposed Subway Station Descriptions......................................................................................................1
Table 2.0 – Above Ground Facilities at the Sheppard Avenue West Station................................................................9
Table 2.1 – Storage Requirements at the Sheppard Avenue West Station ..................................................................11
West Commuter Parking Lot
4.9
Inter-Regional Bus Terminal (north
of Steeles) / Station Building
2.1
Table 3.0 – Above ground Facilities at the Finch West Station ..................................................................................12
Table 3.1 – Parking Lot Storage Requirements at the Finch West Station..................................................................15
Table 3.2 – Passenger Pick-up/Drop-off Storage Requirements at the Finch West Station.......................................15
Table 3.3 – Bus Terminal Storage Requirements at the Finch West Station...............................................................16
The proposed subway extension alignment generally follows the divide between the Black Creek
subwatershed and the Lower West Don River subwatershed within the Humber Watershed. As a
result, surface water is generally conveyed away from each of the proposed station locations to
an outlet to one of the two aforementioned watercourses via the existing sewer networks.
Table 4.0 – Above ground Facilities at the York University Station ..........................................................................17
Table 4.1 –Storage Requirements at the York University Station...............................................................................19
Table 5.0 – Above ground Facilities at the Steeles West Station ................................................................................20
Table 5.1 – East Commuter Parking Lot Storage Requirements at the Steeles West Station......................................22
Table 5.2 – West Commuter Parking Lot Storage Requirements at the Steeles West Station ....................................22
Table 5.3 – Bus Terminal Storage Requirements at the Steeles West Station.............................................................23
With the exception of the Finch West and Steeles West stations where commuter parking lots
and bus terminals are proposed, increases in impervious areas resulting from the undertaking
consist mainly of small entrance / exit buildings. New roads are proposed at the Steeles West
Station but are addressed as part of York Region’s Highway 7 Transitway Environmental
Assessment. The proposed GO Transit platform at the Sheppard West Station will be addressed
under a separate GO Transit Environmental Assessment.
The placement of these permanent facilities with impervious areas may affect the drainage
characteristics and quality of runoff from the affected subwatersheds. To offset these potential
impacts, lot level conveyance and quality controls will be implemented. To address these
potential changes in hydraulic performance, a stormwater management plan for each proposed
site has been prepared and is discussed below.
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway EA
SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
ii
Toronto Transit Commission
1
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 1.1 – Proposed Subway Station Locations
Spadina Subway Extension
Environmental Assessment
1.2
2/7/2006
Stormwater Management Report
STUDY SCOPE
This stormwater management (SWM) report includes the following for each proposed station
location:
•
•
•
Identification of the existing drainage condition;
Proposed Drainage Condition; and
Stormwater Management Plan (Water Quality and Quantity Control, Water Balance, and
Erosion and Sediment Control requirements).
In addition, it is assumed that stormwater management of all underground facilities will be
conducted in accordance with standard building code practice with connections to sanitary
sewers. For above ground facilities, (stations and transit facilities including bus terminals,
commuter parking lots and passenger drop-off / pick-up facilities), downspouts will outlet at
ground level. In the case of substations without roofs, it is assumed that their floor drains will
also outlet at ground level.
1.3
STORMWATER MANAGEMENT DESIGN CRITERIA – CITY OF TORONTO
In accordance with the City of Toronto’s Wet Weather Flow Management Policy (August 2003),
the following (interim) must be addressed during design for all proposed subway stations:
•
•
•
1.3.1
Water Quality;
Water Quantity including erosion control and; and
Water Balance.
Water Quality - Total Suspended Solids (TSS)
The wet weather flow (WWF) water quality target is the long-term average removal of 80% of
the Total Suspended Solids (TSS) on annual loading basis from all runoff leaving the
development site based on the post-development level of imperviousness.
1.3.2
Water Quantity
a) Flood Flow Management Criteria
The required level of peak flow control from the development site shall follow Toronto
and Region Conservation Authority (TRCA) Flood Flow Criteria Map, which indicates
that quantity control should ensure post to pre-development peak flows for 2 to 100-year
return period events. For redevelopment sites < 5 ha, peak flows can be computed using
simplified approach such as the Rational Method and IDF curves. Refer to Appendix A
for a copy of TRCA’s Flood Flow Criteria Map.
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
2
Toronto Transit Commission
3
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Spadina Subway Extension
Environmental Assessment
stringent runoff volume requirement becomes the governing target for the
development site.
b) Erosion Control
The TTC must contact TRCA staff to determine erosion control/geomorphology
requirements for individual development sites in the planning stage (TRCA’s
response has been noted in each section addressing erosion and sediment control).
1. For Rouge River watershed, follow TRCA (Toronto Region Conservation
Authority) erosion control criteria for individual sites, which discharge directly to
and/or are in proximity of natural watercourses;
2. For all new large development blocks, which discharge directly to and/or in
proximity of natural watercourses within other watersheds, the proponents are
required to complete an Erosion Analysis Report to determine the erosion control
criteria for the sites. Please consult TRCA for further details.
3. For new development blocks where it is not feasible (i.e. proposed development is
negligible with respect to the total drainage area of the receiving watercourse) to
complete an Erosion Analysis Report, TRCA typically requires that runoff from a
25 mm storm shall be detained on-site and released over a minimum of 24 hours.
4. For small infill/redevelopment sites < 2 ha, erosion control in the form of
stormwater detention is normally not required, provided the on-site minimum
runoff retention from a 5 mm daily rainfall event is achieved under the Water
Balance Criteria.
c) Regardless of the off-site compensatory/cash-in-lieu option, the minimum on-site
runoff retention requires the proponent to capture all runoff from a small design
rainfall event (typically 5 mm) and restore it on-site through infiltration, evapotranspiration and rainwater reuse.
1.4
PERFORMANCE STANDARDS – CITY OF VAUGHAN
The proposed Steeles West station is located on the boundary between the City of Toronto and
the Region of York, within the City of Vaughan. City staff has indicated that quality control
should be in accordance with TRCA requirements, and that quantity control should ensure post
to pre-development peak flows for 2 to 100-year return period events.
Furthermore, any proposed SWM works north of Steeles Avenue between Jane and Keele Streets
must proceed in accordance with the stormwater management initiative that will be developed as
part of the City of Vaughan’s planned development in this area (OPA 620).
1.5
PERFORMANCE STANDARDS – TORONTO TRANSIT COMMISSION (TTC)
This report also considered design criteria recommendations contained in TTC’s “Design
Standards, Volume 1.” Section 2 provides storm drainage design recommendations. The
following is a summary:
c) Erosion and Sediment Control During Construction
•
The Modified Rational Method may be used to develop hydrographs for the design of
detention storage systems (Section 2.2);
•
For design purposes the storm frequency shall meet the requirements of the approval
authorities (Section 2.4.2.1);
•
Roof storage maximum controlled run-off 42 l/s per hectare of roof area, maximum
ponding depth 150 mm; surface storage maximum ponding depth of 0mm for 1:2 year
storm and 250 mm for 1: 100-Year storm (Section 3.2);
•
Overland flow gradients for parking lots shall be a minimum of 2% and a maximum of
4% (Section 5.2.1).
The City of Toronto Erosion Control Criteria during construction are as follows:
1.3.3
2/7/2006
Stormwater Management Report
•
Regardless of size for all development sites, temporary erosion and sediment
control for construction must be provided on-site.
•
All erosion and sediment control BMPs shall be designed, constructed and
maintained in all development sites in accordance with the “GTA CA’s Erosion &
Sediment Control Guidelines For Urban Construction" as well as City of Toronto
Sewer Use By-Law and/or other City of Toronto requirements on a site by site
basis, where applicable.
Water Balance
a) Retained on-site, to the maximum extent practicable to achieve the same level of
annual volume of overland runoff allowable from the development site under predevelopment (i.e. presently existing site conditions before the new proposed
development) conditions.
b) If the allowable annual runoff volume from the development site under postdevelopment conditions is less than the pre-development conditions, then the more
1.6
PERFORMANCE STANDARDS – TORONTO AND REGION CONSERVATION AUTHORITY
(TRCA)
In accordance with TRCA’s requirements, lot level conveyance controls (parking and roof-top
storage) are to be designed to reduce post development peak flows for 2:100 year return periods
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
4
Toronto Transit Commission
5
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
to pre-development flows. Furthermore, the Toronto and Region Conservation Authority
(TRCA) encourages the use of innovative lot level stormwater management controls. These
practices include maximizing on-site stormwater infiltration, the retention and enhancement of
pervious and vegetative area (tree and shrub plantings, infiltration trenches, grassed swales), the
use of biologically-based pollutant load reduction features (bio-swales, vegetated filter strips)
and the reduction of sediment and nutrient loadings through the development of, for instance,
pollution prevention plans, sediment control during construction, oil-grit separators etc.
Examples of innovative of level controls may be viewed on TRCA’s website
(http://www.trca.on.ca); refer to the Etobicoke / Mimico Creek Strategy document, Chapter 7,
page 184. These measures should be considered and incorporated where possible during detailed
design. TRCA’s Erosion and Sediment Control (ESC) Guidelines - December 2003, will be used
as the basis for developing an Erosion and Sedimentation Control Design Brief during detailed
design.
1.7
Spadina Subway Extension
Environmental Assessment
Allowable
Release Rate:
Where for release rates:
Q=7.7450.762ln(A)
2/7/2006
Stormwater Management Report
Q=11.4681.123ln(A)
Q=17.3811.690ln(A)
Q=22.9732.256ln(A)
Q – unit flow (L/s/ha) – litres per second per hectare
A – area in hectares (ha)
For the Steeles West Station, the ultimate SWM plan will be developed during detail design in
accordance with OPA 620 requirements, and for the purposes of the interim SWM plan proposed
at that Station, storage requirements are based on post to pre peak flow rates for all return
periods.
For all proposed stations addressed in this SWM plan, the rational method was used to calculate
peak flows. A pre-development drainage coefficient “C” of 0.3 was used, and a postdevelopment drainage coefficient “C” value of 0.9 was used. North York IDF curve coefficients
(from the City of Toronto) were used as follows:
ANALYSIS METHODOLOGY
Quantity Control
For each proposed facility, the Rational Method was used to determine the pre-construction
uncontrolled peak flow rate (see Appendix B). The following equation was used:
Coefficient
2-year
5-year
25-year
100-year
a
652.8
840.7
1082
1334
b
4
3
2
2
c
0.786
0.779
0.771
0.771
Q x year = CIA/360
Where:
C - permeability coefficient (unitless):
I - rainfall intensity (mm/hour):
A - catchment area (hectares):
0.3 for open fields was used, 0.9 for new facilities;
based on North York IDF curve data,
Tc = 10 minutes pre, 7 minutes post construction;
area of facility in hectares.
City of Toronto harmonized IDF curves (presently not available) or North York District IDF
curves should be used in the detailed designs.
Storage requirements using the Modified Rational Method have been provided in Appendix C.
For the Finch West Station, release rates for the Humber River Watershed, Sub-Basin 46 have
been provided by TRCA (provided below) and should be confirmed during detail design. Roof
control (Zurn) release rates were considered for the Sheppard and York University Stations since
roof leaders will discharge directly to the ground.
2-year
5-year
25-year
Quality Control
Quality control was not considered for the proposed Sheppard West and York University stations
due to the absence of pollution sources at these sites (commuter parking is only being provided
at the proposed Finch West and Steeles West stations). Proposed quality control for the Finch
and Steeles West stations consists of Oil / Grit Separators (OGS) in a “treatment train” approach
in accordance with the above noted criteria as applicable.
100-year
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
6
Toronto Transit Commission
7
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Spadina Subway Extension
Environmental Assessment
CHAPTER 2.0
Water Balance
Preliminary geotechnical information on the subsurface physical conditions (soil and
groundwater) along the proposed subway route was conducted by Golder Associates Ltd.
(Golder) and documented in their draft report “Geotechnical Investigation Report – Spadina
Subway Extension Environmental Assessment” (December 2005). The following excerpt (page
16) summarizes the typical founding soils for the four proposed subway station base slabs:
Station
Estimated Elevation
of Base Slab (m)
Founding Soil
Soil Type
GO/Sheppard Avenue
180
Silt; Clayey silt (Interstadial)
8; 9
Keele/Finch
175
Clayey Silt to Silty Clay Till;
Clayey Silt (Interstadial)
11; 9
York University
175
Sandy Silt to Sand and Silt Till
12
Steeles Avenue
180
Clayey Silt to Silty Clay Till
11
2/7/2006
Stormwater Management Report
SHEPPARD AVENUE WEST STATION SWM PLAN
The Sheppard West Station, situated entirely within the Downsview Park lands, will be located
at the southwest corner of the Bradford GO Line and Sheppard Avenue. New above ground
facilities that will reduce the overall permeability within the study area include the new subway
station building itself. Impervious areas associated with these new facilities are provided in
Table 2.0. Refer to Exhibit 2.1 for a map of this station location including the existing drainage
condition as identified from OBM maps and a site visit.
Table 2.0 – Above Ground Facilities at the Sheppard Avenue West Station
Facility
Impervious Area Proposed (ha)
New TTC Station Roof
Reference is made in this geotechnical report (page 12) to the average hydraulic conductivity of
1.4E-05 to 3.0E-05 cm/s within the cohesive and glacial till deposits. Although these preliminary
soils investigations indicate soils not conducive to Water Balance measures, measures will need
to be addressed for each station during detail design in accordance with the above noted criteria
where feasible.
On-site SWMP's considered in the following plan include rooftop restrictors (at station
buildings), exfiltration systems (proposed in a “treatment train” approach with oil / grit
separators) and underground storage at the proposed parking lots at Finch and Steeles Stations
(super pipe for the 2-year event). Additional SWMP’s to be considered during detail design
include rainwater harvesting, green roof technologies, absorbent landscaping, pervious pavement
in parking lots and tree plantings and bushes. Additionally, the use of curb and gutter with
catchbasins and exfiltration / infiltration systems should be considered.
0.2
The surface at the existing site drains generally to the north. Utility information provided by the
City indicates that storm water is conveyed easterly along Sheppard Avenue through a series of
storm sewers (900, 1050 mm diameter in the vicinity of the proposed station) eventually draining
to the G. Ross Lord Dam and Reservoir to the north/north-east.
2.1
DESIGN REQUIREMENTS
Design of SWM facilities will be based on the criteria provided by the City of Toronto, the TTC,
and TRCA as summarized in Sections 1.3 to 1.6 of this Report.
2.2
QUALITY CONTROL
Quality control was not considered for the proposed Sheppard West station due to the absence of
pollution sources this site.
2.3
QUANTITY CONTROL
The following summarizes the results of the hydraulic /hydrologic analysis and identifies the
proposed stormwater management plan for each proposed station location.
As indicated in Section 1.7, the Rational Method was used to determine the pre-construction
uncontrolled 2 to 100-year peak flow rates. To ensure that the subject development will not have
a negative impact on downstream conditions, it is necessary to control the post-development
flows for each return period from 2 to 100 years to pre-development flows. For the TTC station
building, rooftop storage is proposed. A separate GO Transit Environmental Assessment will be
conducted for the stormwater management of the proposed new GO Transit platform.
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
8
Toronto Transit Commission
9
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 2.1 – Existing Drainage Conditions at the Proposed Sheppard West Station
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Allowable release rates were provided by TRCA (Section 1.7); however, as downspouts will
outlet at ground level, and as the TTC roof storage maximum controlled run-off is 42 l/s per
hectare (TTC Standard Volume 1, Section 3.2), a maximum allowable release rate was set to (42
l/s) x (0.2 ha) = 8.4 l/s.
Results are summarized in Table 2.1.
Table 2.1 – Storage Requirements at the Sheppard Avenue West Station
900 mm Dia.
1050 mm Dia.
Drains to G.
Ross Lord
R
i
Facility
Area
(ha)
Return
Period
Allowable
Release
Rate (l/s)
Q
Uncontrolled
Pre-Const.
(l/s)
Q
Uncontrolled
Post-Const.
(l/s)
Volume
Required
(m3)
TTC
Station
Building
0.2
2-year
8.4
13.7
49.6
22
0.2
5-year
8.4
19.0
70.0
35
0.2
25-year
8.4
26.6
99.5
53
0.2
100-year
8.4
32.8
122.7
70
The proposed stormwater management plan for this station entails the use of quantity control
through the use of Zurn Roof Control Drains in accordance with previously stated design
criteria.
2.4
WATER BALANCE
As indicated in Section 1.7, the preliminary soils investigations in the vicinity of the Sheppard
Ave. West station indicate soils may not be conducive to water balance measures. However, City
of Toronto water balance requirements in accordance with Section 1.3.3 should be addressed
during detail design.
2.5
EROSION AND SEDIMENT CONTROL
Erosion and Sediment Control will be addressed during detail design in accordance with
applicable criteria in Section 1.3.2 above. During planning, it was confirmed by TRCA that
criteria (c) Section 1.3.2 governs at this location.
Surface Runoff
Existing Sewer
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
10
Toronto Transit Commission
11
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
CHAPTER 3.0
2/7/2006
Stormwater Management Report
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 3.1 – Existing Drainage Conditions at the Proposed Finch West Station
FINCH WEST STATION SWM PLAN
The Finch West Station will be located at the intersection of Finch Avenue and Keele Street.
New above ground facilities that will reduce the overall permeability of the study area include
the new commuter parking lot to the east of Keele Street, the passenger pick –up and drop-off to
the west of Keele Street, and the proposed bus terminal including the new roads. Impervious
areas associated with these new facilities are provided in Table 3.0. Refer to Exhibit 3.1 for a
map of this station location including the existing drainage condition as identified from OBM
maps and a site visit.
Drains to G.
Ross Lord
R
i
900 mm Dia.
Table 3.0 – Above ground Facilities at the Finch West Station
Impervious Area Proposed (ha)
Commuter Parking Lot
2.3
Passenger Pick-Up / Drop-Off
0.3
Bus Terminal / Roads / Station
Building
1.2
According to drainage mosaics provided by the City, the surface at the existing site generally
drains to the east and west from Keele Street, with the exception of a triangular area at the northeast quadrant of the Finch / Keele intersection which also drains to the west as indicated in
Exhibit 3.1. The site is drained by storm sewers, with the area west of Keele street draining
towards the 5000 x 3000 mm CSP under Finch Avenue, ultimately released to the Black Creek;
to the east, storm water is conveyed via storm sewers and creek to the G. Lord Ross Reservoir
and Dam.
3.1
DESIGN REQUIREMENTS
Design of SWM facilities will be based on criteria provided by the City of Toronto, the TTC, and
TRCA as summarized in Sections 1.3 to 1.6 of this Report.
3.2
450 mm Dia.
Facility
Drainage
Boundary
900 mm Dia.
750 mm Dia.
Drains to 3000 x
5000 CSP Under
Finch to Black
Creek
QUALITY CONTROL
Surface Runoff
To address the requirements for quality treatment on the site, oil grit separators are proposed in a
treatment train approach in coordination to include for instance bio-swales and infiltration
systems. Proposed flow patterns are indicated in Exhibit 3.2.
Existing Sewer
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
12
Toronto Transit Commission
13
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 3.2 – Proposed Drainage Conditions at the Proposed Finch West Station
Spadina Subway Extension
Environmental Assessment
3.3
2/7/2006
Stormwater Management Report
QUANTITY CONTROL
For the parking lot, passenger pick-up / drop-off and bus terminal, parking lot conveyance
control is suggested. Results are summarized in Tables 3.1, 3.2, and 3.3.
Drains to G.
Ross Lord
R
i
450 mm Dia.
900 mm Dia.
Table 3.1 – Parking Lot Storage Requirements at the Finch West Station
Facility
Area
(ha)
Return
Period
Allowable
Release
Rate (l/s)
Q
Uncontrolled
Pre-Const. (l/s)
Q
Uncontrolled
Post-Const.
(l/s)
Volume
Required
(m3)
Comm.
Parking
Lot
2.3
2-year
16.4
157.3
570.5
498
2.3
5-year
24.2
218.7
804.7
648
2.3
25-year
36.7
305.5
1144.3
840
2.3
100-year
48.5
376.7
1410.7
1013
Table 3.2 – Passenger Pick-up/Drop-off Storage Requirements at the Finch West Station
Drainage
Boundary
900 mm Dia.
750 mm Dia.
Drains to 3000 x
5000 CSP Under
Finch to Black
Creek
Facility
Area
(ha)
Return
Period
Allowable
Release
Rate (l/s)
Q
Uncontrolled
Pre-Const. (l/s)
Q
Uncontrolled
Post-Const.
(l/s)
Volume
Required
(m3)
Pass.
Pick-Up
DropOff
0.3
2-year
2.6
20.5
74.4
61
0.3
5-year
3.8
28.5
105.0
80
0.3
25-year
5.8
39.9
149.3
103
0.3
100-year
7.7
49.1
184.0
124
Existing Sewer
Proposed Flow
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
14
Toronto Transit Commission
15
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Table 3.3 – Bus Terminal Storage Requirements at the Finch West Station
Facility
Bus
Terminal/
Roads /
Station
Building
Spadina Subway Extension
Environmental Assessment
CHAPTER 4.0
Area
(ha)
Return
Period
Allowable
Release
Rate (l/s)
Q
Uncontrolled
Pre-Const. (l/s)
Q
Uncontrolled
Post-Const.
(l/s)
Volume
Required
(m3)
1.2
2-year
9.1
82.1
297.7
255
1.2
5-year
13.5
114.1
419.9
331
1.2
25-year
20.5
159.4
597.0
429
1.2
100-year
27.1
196.5
736.0
517
2/7/2006
Stormwater Management Report
YORK UNIVERSITY STATION SWM PLAN
The York University Station will be located at the east end of the “commons” within the
University campus. The Subway station will be a below ground facility. New above ground
facilities that will reduce the overall permeability of the study area include the substation
building, as well as two entrances to the subway. Impervious areas associated with these new
facilities are provided in Table 4.0. Refer to Exhibit 4.1 for a map of this station location
including the existing drainage condition as identified from OBM maps and a site visit.
Table 4.0 – Above ground Facilities at the York University Station
Facility
Impervious Area Proposed (ha)
Substation Building and Entrances
0.1
The proposed stormwater management plan for this station entails the use of quantity control
through the use of Zurn Roof Control Drains in accordance with previously stated design
criteria. To further satisfy TTC site drainage requirements (see Section 1.5 above) since no
ponding will be permitted under the 2-year storm event, it is proposed that the post-construction
2-year storm event be captured in a “super-pipe”. Refer to Exhibit 3.2 for a map of this station
location including the proposed drainage condition. It is proposed that Oil / Grit Separators
(OGS) be used in a “treatment train” approach, including exfiltration trenches located in grassed
boulevard areas adjacent to parking lots prior to entry into City sewer system (as the only
available space is in the Hydro Corridor, this will require approval from Ontario Hydro).
Surface water in the vicinity of the proposed facility drains through a series of storm sewers to
the pond at Pond Road, then ultimately to the Black Creek. A ditch inlet was noted in the grassed
area of the “Common”, as well as on the east side of Ian MacDonald Boulevard within the
existing grassed swale.
3.4
Design of SWM facilities will be based on criteria provided by the City of Toronto, the TTC, and
TRCA as summarized in Sections 1.3 to 1.6 of this Report.
WATER BALANCE
4.1
DESIGN REQUIREMENTS
As indicated in Section 1.7, the preliminary soils investigations in the vicinity of the Finch West
station indicate soils may not be conducive to water balance measures. However, City of Toronto
water balance requirements in accordance with Section 1.3.3 should be addressed during detail
design.
Quality control was not considered for the proposed York University station due to the absence
of pollution sources (new facilities include only building roofs) at this site.
3.5
4.3
EROSION AND SEDIMENT CONTROL
Erosion and Sediment Control will be addressed during detail design in accordance with
applicable criteria in Section 1.3.2 above. During planning, it was confirmed by TRCA that
criteria (d) Section 1.3.2 governs at this location, however, TRCA also requested that the runoff
from a 25 mm storm be detained on-site and released over a minimum of 48 hours.
4.2
QUALITY CONTROL
QUANTITY CONTROL
As indicated in Section 1.7, the Rational Method was used to determine the pre-construction
uncontrolled 2 to 100-year peak flow rates. To ensure that the subject development will not have
a negative impact on downstream conditions, it is necessary to control the post-development
flows for each return period from 2 to 100 years to pre-development flows. For the TTC station
building, rooftop storage is proposed and summarized in Table 4.1. Although peak runoff will be
controlled for post to pre for the 2 to 100 year events, York University’s Stormwater
Management Plan should be consulted for any additional requirements prior to detailed design.
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
16
Toronto Transit Commission
17
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 4.1 – Existing Drainage Conditions at the Proposed York University Station
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Allowable release rates were provided by TRCA (Section 1.7); however, as downspouts will
outlet at ground level, and as the TTC roof storage maximum controlled run-off is 42 l/s per
hectare (TTC Standard Volume 1, Section 3.2), a maximum allowable release rate was set to (42
l/s) x (0.1 ha) = 4.2 l/s.
Table 4.1 –Storage Requirements at the York University Station
400 mm Dia.
1800 mm Dia.
Facility
Area
(ha)
Return
Period
Allowable
Release
Rate (l/s)
Q
Uncontrolled
Pre-Const.
(l/s)
Q
Uncontrolled
Post-Const.
(l/s)
Volume
Required
(m3)
TTC
Station
Building
0.1
2-year
4.2
6.8
24.8
11
0.1
5-year
4.2
9.5
35.0
17
0.1
25-year
4.2
13.3
49.8
26
0.1
100-year
4.2
16.4
61.3
35
The proposed stormwater management plan for this station entails the use of quantity control
through the use of Zurn Roof Control Drains in accordance with previously stated design criteria
4.4
Drains to pond
prior to Black
Creek
WATER BALANCE
As indicated in Section 1.7, the preliminary soils investigations in the vicinity of the York
University station indicate soils may not be conducive to water balance measures. However, City
of Toronto water balance requirements in accordance with Section 1.3.3 should be addressed
during detail design.
4.5
EROSION AND SEDIMENT CONTROL
Erosion and Sediment Control will be addressed during detail design in accordance with
applicable criteria in Section 1.3.2 above. During planning, it was confirmed by TRCA that
criteria (c) Section 1.3.2 governs at this location.
Surface Runoff
Existing Sewer
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
18
Toronto Transit Commission
19
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
CHAPTER 5.0
2/7/2006
Stormwater Management Report
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 5.1 – Existing Drainage Conditions at the Proposed Steeles West Station
STEELES WEST STATION SWM PLAN
The Steeles West Station will be located at the intersection of Steeles Avenue and Northwest
Gate. New above ground facilities that will reduce the overall permeability of the study area
include two new commuter parking lots located within the Hydro corridor north of Steeles
Avenue, one bus terminal located north of Steeles Avenue including passenger pick-up and dropoff facilities and entrances. Impervious areas associated with these new facilities are provided in
Table 5.0. One bus terminal is to be located south of Steeles Avenue utilizing an existing
parking lot, and thereby not increasing the ground imperviousness. Refer to Exhibit 5.1 for a
map of this station location including the existing drainage condition as identified from OBM
maps and a site visit.
Table 5.0 – Above ground Facilities at the Steeles West Station
Facility
Impervious Area Proposed (ha)
New East Commuter Parking Lot
5.2
New West Commuter Parking Lot including
Passenger Pick-Up and Drop-Off
4.9 *
New Inter-Regional Bus Terminals (north of
Steeles Avenue) / Station Buildings
2.1
New Inter-Regional Bus Terminal (south of
Steeles Avenue) / Station Buildings
Area presently paved
* Includes a portion of facilities included in York Regions Highway 7 Transitway EA.
Drains to pond
north of Steeles
at Jane.
1650 – 1800 mm Dia.
1500 mm Dia.
Drains to pond
south of Steels
at Jane.
Presently the subject land, north of Steeles and south of the Hydro corridor, is an open field
where Northwest Gate intersects Steeles Avenue at an unsignalized “T” intersection. Surface
drainage in the area of the proposed facility is to the south, to two sets of existing storm sewers,
one under Steeles Avenue, and one just north of the right-of-way. The storm sewer under Steeles
Avenue (600 to 1500 mm diameter) drains to TRCA’s pond at Black Creek Pioneer Village; to
the north to the right-of-way, the storm sewer (1650 to 1800 mm diameter) drains to a pond
north of Steeles Avenue near Jane Street. It is assumed that the building to the east of the
proposed facility manages it’s own stormwater. Therefore the property boundary of the proposed
parking facilities coincides with the drainage boundaries.
Surface Runoff
Existing Sewer
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
20
Toronto Transit Commission
21
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
5.1
2/7/2006
Stormwater Management Report
DESIGN REQUIREMENTS
Design of SWM facilities will be based on the criteria provided by the City of Toronto, the TTC,
TRCA and the City of Vaughan, as summarized in Sections 1.3 to 1.6 of this Report.
According to TRCA, the existing stormwater management pond (CFN 8133, TRCA Pond File
42.0) located north of Steeles at Jane Street is inadequate by present day standards, and there is
little room available to expand the pond for the redevelopment of the industrial area to the north
of Steeles Avenue including the Steeles West Station. The pond is presently a peak flow
attenuation facility only. Although it is not presently possible within the scope of this study to
provide a definitive SWM plan for the Steeles West Station, a detailed SWM plan for the Steeles
West Station will need to be integrated into a comprehensive stormwater Management master
plan, once developed, in accordance with development (OPA 620) in the area.
5.2
2/7/2006
Stormwater Management Report
Facility
Area
(ha)
Return
Period
Q Uncontrolled
Pre-Const. (l/s)
Q Uncontrolled
Post-Const. (l/s)
Volume Required
(m3)
West
Parking
Lot
4.9
2-year
335.2
1215.4
411
4.9
5-year
465.8
1714.4
565
4.9
25-year
650.9
2437.8
780
4.9
100-year
802.5
3005.5
961
Table 5.3 – Bus Terminal Storage Requirements at the Steeles West Station
Facility
Area
(ha)
Return
Period
Q Uncontrolled
Pre-Const. (l/s)
Q Uncontrolled
Post-Const. (l/s)
Volume Required
(m3)
2.1
2-year
143.7
520.9
176
2.1
5-year
199.6
734.8
242
2.1
25-year
279.0
1044.8
334
2.1
100-year
343.9
1288.1
412
QUALITY CONTROL
To address the interim requirements for quality treatment on the site (prior to a developed
Master SWM Plan for the area in accordance with OPA 620), oil grit separators are proposed in
a treatment train approach, to include for instance bio-swales and infiltration systems. Proposed
flow patterns are indicated in Exhibit 5.2.
5.3
Spadina Subway Extension
Environmental Assessment
Bus
Terminal/
Station
Building
QUANTITY CONTROL
For the parking lot, passenger pick-up / drop-off and bus terminal, in-lieu of a definitive SWM
Master Plan for the area, interim parking lot conveyance control is suggested. Results are
summarized in Tables 5.1, 5.2, and 5.3. Although the east and west commuter parking lot areas
approach and slightly exceed the criteria for Rational Method calculations (Section 1.3.2 above)
the Rational Method was used since some portion of these facilities are actually addressed in
York Region’s Highway 7 Transitway EA. Furthermore, the impacts from new roads will also be
addressed separately through York Region’s Hwy 7 Transitway Environmental Assessment.
Table 5.1 – East Commuter Parking Lot Storage Requirements at the Steeles West Station
To further satisfy TTC site drainage requirements (see Section 1.5 above) since no ponding will
be permitted under the 2-year storm event, it is proposed that the post-construction 2-year storm
event be captured in a “super-pipe” or in swales or depressions prior to release. Refer to Exhibit
5.2 for a map of this station location including the proposed drainage condition. It is proposed
that this interim solution (ultimate SWM solution to be part of the SWM Master Plan in
accordance with OPA 620), Oil / Grit Separators (OGS) be used in a “treatment train” approach,
including exfiltration trenches located in grassed boulevard areas adjacent to parking lots).
5.4
WATER BALANCE
As indicated in Section 1.7, the preliminary soils investigations in the vicinity of the Steeles
West station indicate soils may not be conducive to water balance measures. However, City of
Toronto water balance requirements according to Section 1.3.3 will be addressed in detail
design.
Facility
Area
(ha)
Return
Period
Q Uncontrolled
Pre-Const. (l/s)
Q Uncontrolled
Post-Const. (l/s)
Volume Required
(m3)
East
Parking
Lot
5.2
2-year
355.7
1289.8
450
5.2
5-year
494.4
1819.4
599
5.5
5.2
25-year
690.8
2587.0
828
5.2
100-year
851.7
3189.5
1020
Erosion and Sediment Control will be addressed during detail design in accordance with
applicable criteria in Section 1.3.2 above. During planning, it was confirmed by TRCA that
criteria (d) Section 1.3.2 governs at this location, however, TRCA also requested that the runoff
from a 25 mm storm be detained on-site and released over a minimum of 48 hours.
Table 5.2 – West Commuter Parking Lot Storage Requirements at the Steeles West Station
EROSION AND SEDIMENT CONTROL
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
22
Toronto Transit Commission
23
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
2/7/2006
Stormwater Management Report
Exhibit 5.2 – Proposed Drainage Conditions at the Proposed Steeles West Station
Spadina Subway Extension
Environmental Assessment
CHAPTER 6.0
2/7/2006
Stormwater Management Report
CONSTRUCTION IMPACTS AND MITIGATION AND
MONITORING
During construction activities including dewatering, erosion and sedimentation potential will be
addressed.
Governmental documentation related to erosion control and sedimentation exists in the following
three forms: legislation, guidelines and by-laws. Guidelines used within TRCA’s jurisdiction
include current editions of the following:
Drains to pond
north of Steeles
at Jane.
1650 – 1800 mm Dia.
•
MNR Technical Guideline: Erosion and Sediment Control;
•
GTA Conservation Authorities Erosion & Sediment Control Guidelines for Urban
Construction;
•
City of Toronto Sewer Use B-Law; and,
•
MTO Drainage Management Manual.
Mitigation will be addressed in contract documents according to TRCA’s Erosion and
Sedimentation guidelines with explains the design, function, installation procedure, maintenance
procedure, and removal procedure for each of the following ESC measures including, but not
limited to sediment traps, interceptor swales/dykes, sediment control fences, straw bales, sodding
etc.
Prior to construction, the contractor is required to submit comprehensive environmental controls
and methods plan to address, among other elements, effluent (water control) as per TTC’s
Master Specification 05-06-28 – Section 01575 – subsection 6. The effectiveness of this plan is
monitored during a demonstration of the process that is undertaken before the Work can
commence on site. A representative of TTC will undertake monitoring of plan compliance.
1500 mm Dia.
Drains to Pond
south of Steeles
at Jane.
The construction process will result in exposed soil in areas such as the Hydro corridors during
the construction of the commuter parking lots or the Downsview lands during the open cut
construction of the running structure. Sediment and erosion control measures will be inspected
regularly by TTC to ensure that these measures are maintained in proper working order until all
areas are fully stabilized.
Existing Sewer
Proposed Flow
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
URS Canada Inc.
24
Toronto Transit Commission
25
Toronto Transit Commission
Spadina Subway Extension
Environmental Assessment
CHAPTER 7.0
2/7/2006
Stormwater Management Report
CONCLUSIONS
The preliminary analysis as summarized in this report indicates that the proposed stormwater
management plan for each of the 3 proposed subway stations, namely Sheppard West, Keele
Street, and York University Stations will satisfy design requirements of the TTC, the City of
Toronto and TRCA. The SWM plan for the Steeles West Station will require further
development during detail design in accordance with a SWM Master Plan to be developed in
response to development north of Steeles Avenue.
Further refinements to this plan will be required during the detailed design phase of the subway
extension project.
O:\1-33015347 Spadina Subway EA\Documents\03 Reports\99 Draft Versions\EA\Appendix\Appendix Y Stormwater Management\SWM Final Report Feb 7 06\013006 TTC Spadina Subway
EA SWM Rpt.doc
URS Canada Inc.
26
Toronto Transit Commission
APPENDICES
APPENDIX A
TRCA’s Flood Flow Criteria Map
APPENDIX B
RATIONAL METHOD CALCULATIONS
URS Canada Inc
Spadina Subway Ext. SWM
Sheppard
URS Canada Inc
Spadina Subway Ext. SWM
Predevelopment
Finch Parking
2-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
"C" =
0.30
Tc = 10.00
AC = 0.060
2.78*AC = 0.167
Rainfall Intensity = 82.02
Runoff =
13.7
5-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
"C" =
0.30
Tc = 10.00
AC = 0.060
2.78*AC = 0.167
Rainfall Intensity = 113.99
Runoff =
19.0
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
l/s
2-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
"C" =
0.30
Tc = 10.00
AC = 0.690
2.78*AC = 1.918
Rainfall Intensity = 82.02
Runoff =
Rainfall Intensity
Coefficients
York Region
5 Year Storm
840.7
a=
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
mm/hr
l/s
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
218.7
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.060
2.78*AC = 0.167
Rainfall Intensity = 196.38 mm/hr
32.8
min
25-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.690
2.78*AC = 1.918
Rainfall Intensity = 159.29 mm/hr
Runoff =
Runoff =
Rainfall Intensity
Coefficients
York Region
2 Year Storm
652.8
a=
b=
4.00
c=
0.786
ha
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.060
2.78*AC = 0.167
Rainfall Intensity = 159.29 mm/hr
26.6
157.3
5-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
"C" =
0.30
Tc = 10.00
AC = 0.690
2.78*AC = 1.918
Rainfall Intensity = 113.99
Runoff =
Runoff =
Predevelopment
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
305.5
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.690
2.78*AC = 1.918
Rainfall Intensity = 196.38 mm/hr
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
Runoff =
1 of 8
376.7
l/s
2 of 8
URS Canada Inc
Spadina Subway Ext. SWM
Finch PPUDO
URS Canada Inc
Spadina Subway Ext. SWM
Predevelopment
Finch Bus Terminal
2-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
"C" =
0.30
Tc = 10.00
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 82.02
Runoff =
20.5
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
2-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
"C" =
0.30
Tc = 10.00
AC = 0.360
2.78*AC = 1.001
Rainfall Intensity = 82.02
Runoff =
28.5
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
114.1
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 196.38 mm/hr
49.1
mm/hr
25-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.360
2.78*AC = 1.001
Rainfall Intensity = 159.29 mm/hr
Runoff =
Runoff =
min
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 159.29 mm/hr
39.9
82.1
5-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
"C" =
0.30
Tc = 10.00
AC = 0.360
2.78*AC = 1.001
Rainfall Intensity = 113.99
Runoff =
Runoff =
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
l/s
Runoff =
5-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
"C" =
0.30
Tc = 10.00
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 113.99
Predevelopment
Rainfall Intensity
Coefficients
York Region
100 Year Storm
1334
a=
b=
2.00
c=
0.771
159.4
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.360
2.78*AC = 1.001
Rainfall Intensity = 196.38 mm/hr
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
Runoff =
3 of 8
196.5
l/s
4 of 8
URS Canada Inc
Spadina Subway Ext. SWM
URS Canada Inc
Spadina Subway Ext. SWM
Steeles East Parking
York University
Predevelopment
2-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
"C" =
0.30
Tc = 10.00
AC = 0.030
2.78*AC = 0.083
Rainfall Intensity = 82.02
Runoff =
6.8
5-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
"C" =
0.30
Tc = 10.00
AC = 0.030
2.78*AC = 0.083
Rainfall Intensity = 113.99
Runoff =
9.5
Rainfall Intensity
Coefficients
York Region
2 Year Storm
652.8
a=
b=
4.00
c=
0.786
ha
min
mm/hr
13.3
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
16.4
Runoff =
355.7
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
l/s
5-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
"C" =
0.30
Tc = 10.00
AC = 1.560
2.78*AC = 4.337
Rainfall Intensity = 113.99
Runoff =
494.4
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
l/s
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
25-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
ha
"C" =
0.30
Tc = 10.00 min
AC = 1.560
2.78*AC = 4.337
Rainfall Intensity = 159.29 mm/hr
Runoff =
690.8
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.030
2.78*AC = 0.083
Rainfall Intensity = 196.38 mm/hr
Runoff =
2-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
"C" =
0.30
Tc = 10.00
AC = 1.560
2.78*AC = 4.337
Rainfall Intensity = 82.02
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.030
2.78*AC = 0.083
Rainfall Intensity = 159.29 mm/hr
Runoff =
Predevelopment
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
100-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
ha
"C" =
0.30
Tc = 10.00 min
AC = 1.560
2.78*AC = 4.337
Rainfall Intensity = 196.38 mm/hr
Runoff =
851.7
Rainfall Intensity
Coefficients
York Region
100 Year Storm
1334
a=
b=
2.00
c=
0.771
l/s
l/s
5 of 8
6 of 8
URS Canada Inc
Spadina Subway Ext. SWM
URS Canada Inc
Spadina Subway Ext. SWM
Steeles West Parking Predevelopment
Steeles Bus Terminal Predevelopment
2-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
"C" =
0.30
Tc = 10.00
AC = 1.470
2.78*AC = 4.087
Rainfall Intensity = 82.02
Runoff =
335.2
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
2-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
"C" =
0.30
Tc = 10.00
AC = 0.630
2.78*AC = 1.751
Rainfall Intensity = 82.02
Runoff =
465.8
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
199.6
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
ha
"C" =
0.30
Tc = 10.00 min
AC = 1.470
2.78*AC = 4.087
Rainfall Intensity = 196.38 mm/hr
802.5
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.630
2.78*AC = 1.751
Rainfall Intensity = 159.29 mm/hr
Runoff =
Runoff =
mm/hr
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
ha
"C" =
0.30
Tc = 10.00 min
AC = 1.470
2.78*AC = 4.087
Rainfall Intensity = 159.29 mm/hr
650.9
143.7
5-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
"C" =
0.30
Tc = 10.00
AC = 0.630
2.78*AC = 1.751
Rainfall Intensity = 113.99
Runoff =
Runoff =
min
l/s
Runoff =
5-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
"C" =
0.30
Tc = 10.00
AC = 1.470
2.78*AC = 4.087
Rainfall Intensity = 113.99
Rainfall Intensity
Coefficients
York Region
2 Year Storm
652.8
a=
b=
4.00
c=
0.786
ha
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
279.0
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
ha
"C" =
0.30
Tc = 10.00 min
AC = 0.630
2.78*AC = 1.751
Rainfall Intensity = 196.38 mm/hr
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
Runoff =
7 of 8
343.9
l/s
8 of 8
URS Canada Inc
Spadina Subway Ext. SWM
Sheppard
URS Canada Inc
Spadina Subway Ext. SWM
Post Development
Finch Parking
2-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
"C" =
0.90
Tc =
7.00
AC = 0.180
2.78*AC = 0.500
Rainfall Intensity = 99.14
Runoff =
49.6
5-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
"C" =
0.90
Tc =
7.00
AC = 0.180
2.78*AC = 0.500
Rainfall Intensity = 139.84
Runoff =
70.0
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
l/s
2-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
"C" =
0.90
Tc =
7.00
AC = 2.070
2.78*AC = 5.755
Rainfall Intensity = 99.14
Runoff =
Rainfall Intensity
Coefficients
York Region
5 Year Storm
840.7
a=
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
122.7
min
mm/hr
l/s
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
l/s
1144.3
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
ha
"C" =
0.90
Tc =
7.00
min
AC = 2.070
2.78*AC = 5.755
Rainfall Intensity = 245.15 mm/hr
Runoff =
1 of 8
804.7
25-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
ha
"C" =
0.90
Tc =
7.00
min
AC = 2.070
2.78*AC = 5.755
Rainfall Intensity = 198.84 mm/hr
Runoff =
100-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
ha
"C" =
0.90
Tc =
7.00
min
AC = 0.180
2.78*AC = 0.500
Rainfall Intensity = 245.15 mm/hr
Runoff =
Rainfall Intensity
Coefficients
York Region
2 Year Storm
652.8
a=
b=
4.00
c=
0.786
ha
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
0.20
ha
"C" =
0.90
Tc =
7.00
min
AC = 0.180
2.78*AC = 0.500
Rainfall Intensity = 198.84 mm/hr
99.5
570.5
5-Year Pre-Development Peak Flow
Rational Method
Area =
2.30
"C" =
0.90
Tc =
7.00
AC = 2.070
2.78*AC = 5.755
Rainfall Intensity = 139.84
Runoff =
Runoff =
Post Development
1410.7
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
2 of 8
URS Canada Inc
Spadina Subway Ext. SWM
Finch PPUDO
URS Canada Inc
Spadina Subway Ext. SWM
Post Development
Finch Bus Terminal
2-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
"C" =
0.90
Tc =
7.00
AC = 0.270
2.78*AC = 0.751
Rainfall Intensity = 99.14
Runoff =
74.4
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
2-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
"C" =
0.90
Tc =
7.00
AC = 1.080
2.78*AC = 3.002
Rainfall Intensity = 99.14
Runoff =
105.0
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
419.9
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
ha
"C" =
0.90
Tc =
7.00
min
AC = 0.270
2.78*AC = 0.751
Rainfall Intensity = 245.15 mm/hr
184.0
mm/hr
25-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
ha
"C" =
0.90
Tc =
7.00
min
AC = 1.080
2.78*AC = 3.002
Rainfall Intensity = 198.84 mm/hr
Runoff =
Runoff =
min
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
ha
"C" =
0.90
Tc =
7.00
min
AC = 0.270
2.78*AC = 0.751
Rainfall Intensity = 198.84 mm/hr
149.3
297.7
5-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
"C" =
0.90
Tc =
7.00
AC = 1.080
2.78*AC = 3.002
Rainfall Intensity = 139.84
Runoff =
Runoff =
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
l/s
Runoff =
5-Year Pre-Development Peak Flow
Rational Method
Area =
0.30
"C" =
0.90
Tc =
7.00
AC = 0.270
2.78*AC = 0.751
Rainfall Intensity = 139.84
Post Development
Rainfall Intensity
Coefficients
York Region
100 Year Storm
1334
a=
b=
2.00
c=
0.771
597.0
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
1.20
ha
"C" =
0.90
Tc =
7.00
min
AC = 1.080
2.78*AC = 3.002
Rainfall Intensity = 245.15 mm/hr
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
Runoff =
3 of 8
736.0
l/s
4 of 8
URS Canada Inc
Spadina Subway Ext. SWM
URS Canada Inc
Spadina Subway Ext. SWM
Steeles East Parking
York University
Post Development
2-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
"C" =
0.90
Tc =
7.00
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 99.14
Runoff =
24.8
5-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
"C" =
0.90
Tc =
7.00
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 139.84
Runoff =
35.0
Rainfall Intensity
Coefficients
York Region
2 Year Storm
652.8
a=
b=
4.00
c=
0.786
ha
min
mm/hr
49.8
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
61.3
Runoff =
1289.8
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
l/s
5-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
"C" =
0.90
Tc =
7.00
AC = 4.680
2.78*AC = 13.010
Rainfall Intensity = 139.84
Runoff =
1819.4
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
l/s
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
25-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
ha
"C" =
0.90
Tc =
7.00
min
AC = 4.680
2.78*AC = 13.010
Rainfall Intensity = 198.84 mm/hr
Runoff =
2587.0
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
ha
"C" =
0.90
Tc =
7.00
min
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 245.15 mm/hr
Runoff =
2-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
"C" =
0.90
Tc =
7.00
AC = 4.680
2.78*AC = 13.010
Rainfall Intensity = 99.14
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
0.10
ha
"C" =
0.90
Tc =
7.00
min
AC = 0.090
2.78*AC = 0.250
Rainfall Intensity = 198.84 mm/hr
Runoff =
Post Development
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
100-Year Pre-Development Peak Flow
Rational Method
Area =
5.20
ha
"C" =
0.90
Tc =
7.00
min
AC = 4.680
2.78*AC = 13.010
Rainfall Intensity = 245.15 mm/hr
Runoff =
3189.5
Rainfall Intensity
Coefficients
York Region
100 Year Storm
1334
a=
b=
2.00
c=
0.771
l/s
l/s
5 of 8
6 of 8
URS Canada Inc
Spadina Subway Ext. SWM
URS Canada Inc
Spadina Subway Ext. SWM
Steeles West Parking Post Development
Steeles Bus Terminal Post Development
2-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
"C" =
0.90
Tc =
7.00
AC = 4.410
2.78*AC = 12.260
Rainfall Intensity = 99.14
Runoff =
1215.4
Rainfall Intensity
Coefficients
York Region
2 Year Storm
a=
652.8
b=
4.00
c=
0.786
ha
min
mm/hr
2-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
"C" =
0.90
Tc =
7.00
AC = 1.890
2.78*AC = 5.254
Rainfall Intensity = 99.14
Runoff =
1714.4
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
Rainfall Intensity
Coefficients
York Region
5 Year Storm
a=
840.7
b=
3.00
c=
0.779
ha
min
mm/hr
734.8
l/s
Rainfall Intensity
Coefficients
York Region
25 Year Storm
a=
1082
b=
2.00
c=
0.771
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
ha
"C" =
0.90
Tc =
7.00
min
AC = 4.410
2.78*AC = 12.260
Rainfall Intensity = 245.15 mm/hr
3005.5
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
ha
"C" =
0.90
Tc =
7.00
min
AC = 1.890
2.78*AC = 5.254
Rainfall Intensity = 198.84 mm/hr
Runoff =
Runoff =
mm/hr
l/s
25-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
ha
"C" =
0.90
Tc =
7.00
min
AC = 4.410
2.78*AC = 12.260
Rainfall Intensity = 198.84 mm/hr
2437.8
520.9
5-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
"C" =
0.90
Tc =
7.00
AC = 1.890
2.78*AC = 5.254
Rainfall Intensity = 139.84
Runoff =
Runoff =
min
l/s
Runoff =
5-Year Pre-Development Peak Flow
Rational Method
Area =
4.90
"C" =
0.90
Tc =
7.00
AC = 4.410
2.78*AC = 12.260
Rainfall Intensity = 139.84
Rainfall Intensity
Coefficients
York Region
2 Year Storm
652.8
a=
b=
4.00
c=
0.786
ha
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
1044.8
l/s
100-Year Pre-Development Peak Flow
Rational Method
Area =
2.10
ha
"C" =
0.90
Tc =
7.00
min
AC = 1.890
2.78*AC = 5.254
Rainfall Intensity = 245.15 mm/hr
Rainfall Intensity
Coefficients
York Region
100 Year Storm
a=
1334
b=
2.00
c=
0.771
l/s
Runoff =
7 of 8
1288.1
l/s
8 of 8
APPENDIX C
MODIFIED RATIONAL METHOD STORAGE
CALCULATIONS